This is for all the history buffs out there who want to know all about what engines powered what and was available in what years.

This information is culled from an official 1984 Ford LTL-9000 brochure:

DIESEL ENGINE CHOICES
Standard: Cummins NTC-300 (available in California under the NTCC-300 designation) - 300 hp @ 2,100 rpm
Optional:
Cummins Formula 300 - 300 hp @ 1,800 rpm (also with optimized aftercooling)
Cummins NTC-350 - 350 hp @ 2,100 rpm (also available for California delivery as the NTCC-350)
Cummins Formula 350 - 350 hp @ 1,800 rpm
Cummins NTC-400 - 400 hp @ 2,100 rpm (also available for California delivery as the NTCC-400)
Cummins Formula 400 - 400 hp @ 1,800 rpm
Detroit Diesel 8V-92TA - 400 hp @ 2,100 rpm (also available for California delivery as the 8V-92TAC)
Caterpillar 3406B Economy - 310 hp @ 1,800 rpm
Caterpillar 3406B - 310 hp @ 2,100 rpm
Caterpillar 3406B Economy - 350 hp @ 1,800 rpm
Caterpillar 3406B - 350 hp @ 2,100 rpm
Caterpillar 3406B Economy - 400 hp @ 1,800 rpm
Caterpillar 3406B - 400 hp @ 2,100 rpm (also available for California delivery)

Standard transmission: Fuller Roadranger RT-11610 10-speed direct-drive (with Spicer 1760 main/1610 interaxle driveline)
Optional transmissions:
Fuller Roadranger RT-11609A 9-speed direct-drive
Fuller Roadranger RT-14609A 9-speed direct-drive
Fuller Roadranger RT-14610 10-speed direct-drive
Fuller Roadranger RTO-11613 13-speed overdrive
Fuller Roadranger RTO-14613 13-speed overdrive
Fuller Roadranger RTO-14615 15-speed overdrive
Allison HT-740 4-speed automatic
Allison HT-754CR 5-speed close-ratio automatic
Allison HT-750DR 5-speed deep-ratio automatic

~Ben (FordMan1981)